Summary: In the mid-1980s we carried out a prospective study of early pregnancy in which we enrolled 221 health women who were planning to become pregnant. These women collected daily urine specimens for up to six months. We've assayed these specimens to describe the hormonal events of the menstrual cycle and early pregnancy. 155 women became clinically pregnant during the study, while 44 had pregnancies that ended so early that the pregnancies were detectable only by assay of urinary human chorionic gonadotropin. This unique study has been called a landmark, and continues to provide a rich resource for the description of the earliest stages of pregnancy. (More than 30,000 urine samples are still being stored.) We've published 50 papers from this study over the past two decades, some of which have led to new understanding of the fundamental processes of conception and early pregnancy. In addition, we have continued to make use of large population registries in order to pursue basic questions on pregnancy and maternal and infant health. We have worked especially closely with Norwegian colleagues in the analysis of the Norwegian Medical Birth Registry. Last year's progress. We are conducting a study of prenatal exposures and the subsequent risk of cerebral palsy, based within the two national birth cohorts of Norway and Denmark. This study, in collaboration with Norwegian and Danish researchers, includes 350 children with cerebral palsy whose mothers were enrolled in the two birth cohorts. This is by far the largest cohort study of cerebral palsy ever conducted, and allows biological specimens collected during pregnancy to be used to identify exposures and early biological changes (such as inflammation) that may lead to cerebral palsy. Building on reproductive findings reported earlier from data from the Medical Birth Registry of Norway, we linked these data to the Norwegian social insurance scheme to identify cases of cerebral palsy and to databases of Statistics Norway to identify relatives. Our purpose was to use these data from a large population based cohort to systematically investigate recurrence of cerebral palsy among twins and first, second, and third degree relatives and thus to shed light on patterns of inheritance. We saw that people born into families in which someone already has cerebral palsy are themselves at elevated risk, depending on degree of relatedness. The patterns of risk suggest multifactorial inheritance. These data offer additional suggestion that the underlying causes of cerebral palsy extend beyond clinical management of delivery.